<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="/js/vue.js"></script>
  <style>
    #app{
        width: 600px;
        margin: 40px auto;
        text-align: center;
    }
  </style>
</head>
<body>
  <div id="app">
      <h2>当前计数器的值为：{{num}}</h2>
      <counter v-on:counter-add="num++"></counter>
  </div>
<br>
  <script>
    Vue.component('counter',{
        template:'<button @click="add">计数器</button>',
        methods: {
            add:function(){
                this.$emit('counter-add')
            }
        },
    })
   let app = new Vue({
   el:"#app",
   data:{ 
    num:0
      },
    methods:{
        handleAdd:function(){
            this.num++
        }
    }
    })
  </script>
</body>
</html>